System for automatic injection of coolant into thermal recovery wells



March 25, 1969 G. R. HOLLABAUGH 3,434,534

SYSTEM FOR AUTOMATIC INJECTION OF COOLANT INTO THERMAL RECOVERY WELLS Filed DSC. 26, 1967 Mill HNI ll lV/ INVENTOR GEORGE R. HOLLABUGH ATTORNEY United States Patent U.S. Cl. 166-53 10 Claims ABSTRACT OF THE DISCLOSURE This specification discloses:

A system for the automatic injection of a coolant into a thermal recovery well to control downhole temperatures. A tubing string provides for the withdrawal of products of the thermal recovery procedure from the well. A conduit mounted on the tubing string is filled with a heat-expansible fluid. The change in pressure of the fluid, by its expansion at certain temperatures, in this conduit is a signal to begin introduction of coolant into the well. For example, a pressure relief valve may be connected to the conduit and it remains closed when the temperature within the well is less than a specified temperature. The valve opens at an increased pressure when the fluid within the conduit expands to reflect temperatures greater than the specified temperature. The open valve generates a signal as a change in pressure by venting fluid from the conduit into the well. Flow control means, upon occurrence of this signal, introduce a coolant into the well to control downhole temperatures.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to systems which are used with production wells involved in thermal recovery processes. More particularly, it relates to systems for automatically introducing a coolant into these wells in order to control downhole temperatures.

Description of the prior a-rt Thermal recovery techniques, in which hydrocarbons are produced from carbonaceous formations such as oil sands, tar sands, oil shales, and the like by the application of heat thereto, are becoming increasingly prevalent in the oil industry. Perhaps the most widely used thermal recovery procedure involves in situ combustion or fire flooding. In a typical lire ood, a combustion zone is established in the formation and propagated therethrough by the injection of a combustion supporting gas through a suitable injection well. As the combustion supporting gas is injected, products of combustion and other heated fluids in the stratum are forced away from the injection well toward a production well which is arranged to withdraw these products to the earths surface.

In fire ooding, the failure of downhole well equipment results from the high temperatures which are sometimes reached in the production wells. These high temperatures usually are caused by appearance of the flame front in the production well. However, high temperatures can occur by burning in the well of hot produced fluids from the formation. By either cause, these high temperatures cause deterioration or failure of the well equipment such as the liner, casing, or tubing string. In some instances, high temperatures could cause an explosion within the well.

In order to overcome the deleterious effects of such high temperatures, a coolant such as water may be introduced into the production well in order to control downhole temperatures and maintain them at or below a preice selected level. The indiscriminate injection of coolant into the well has obvious disadvantages. Therefore, the coolant is introduced normally only in response to characteristics indicative of the approach of undesirably high bottomhole temperatures. One common expedient is to monitor the temperature of the production effluent at the wellhead and inject water into the well when a significant product temperature rise is noted. Techniques such as these are not always as effective as might be desired. For example, a burn-through may occur in only a small section and cause very localized high temperatures because of the relatively high temperature gradients caused yby poor heat transfer conditions which usually exist within in situ combustion production wells. The poor heat transfer conditions within such wells are due to the predominantly gaseous nature of the production uids. For example, a temperature measurement carried out in a typical in situ combustion production well revealed a normal wellhead temperature of about 275 F. At the same time, the bottomhole temperature at 1200 feet was about 800 F. In order to offset such high temperature gradients it has been proposed to position a temperature sensing element in the lower portion of the production tubing string. However, the sensing element in this position is subject to early failure by being exposed to the highly abrasive action of the fluids within the tubing string.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a system for automatically introducing a coolant into a production well opened to a production interval in a carbonaceous formation from which are recovered the products derived from a thermal recovery procedure. A tubing string in the well has an inlet therein and is arranged for the withdrawal of the products from the formation to the earths surface. A conduit is mounted on the tubing string and has its lower extremity sealed to fluids. A heat-expansible fluid fills the conduit. The change in pressure of the fluid in the conduit, by its expansion at certain temperatures, acts through a pressure sensitive means to produce a signal to begin introduction of coolant into the well. Flow control means, upon occurrence of this signal, introduce a coolant into the well to control downhole temperatures.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, the figure is an illustration partially in section of a production well installation embodying the system of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS In the figure there is shown a well 11 extending from the earths surface 12 into a carbonaceous formation 13 which resides beneath an overburden 14. The formation 13 may be of any geological origin wherein thermal recovery procedures are practiced for the recovery of hydrocarbonous products. For example, the formation 13 may be heavy oil sands, tar sands, and like formations in which heat energy is used for the recovery of hydrocarbonous products.

The well 11 is completed with a casing 16 which extends downwardly 4through the overburden 14 and terminates within the formation 13. The casing 16 is sealed to the overburden 14 and the upper portion of the formation 13 by cement sheath 17. Perforations 18 within casing 16 provide a fluid entry, or production interval, from the interior of the well 11 into the formation 13.

The products from the formation 13 flow through the perforations 18 into the Well 11 and then are withdrawn with a tubing string 19 which extends downwardly from the earths surface through the casing 16. The tubing string 19 passes upwardly from the Well 11 through a wellhead assembly 21. The products from the formation 13 may be passed from the tubing string 19 to any surface-disposed facility.

The described completion of the well 11 is provided as an illustration, and any of the many types of well completions known to those skilled in the art may be ernployed with equal facility for the recovery of products produced by thermal recovery procedures.

A conduit 22 is mounted in juxtaposition with the tubing string 19 within the well 11. The conduit 22 preferably is secured to the tubing string 19 by mounting straps 23. The conduit 22 is sealed at its lower end. Although the conduit 22 may be made of any pressure-resistance material, it is preferable to be made of stainless steel. As a result, a fluid Within the conduit 22 may be contained therein under pressure by surface-disposed valve mechanisms. A heat-expansive fluid, preferably water, fills the conduit 22. However, any fluid which expands upon temperature increases may be used.

The conduit 22 is connected to a pressure sensor 24 and also through suitable piping 26 to a check valve 27, a pump 29 and to a tank 28. The tank 28 contains a supply of coolant which will be introduced into the well 11 upon elevated temperatures being generated therein by thermal recovery procedures conducted in the formation 13. The coolant is usually water but other fluids may be used, if desired. A T 31 in piping 26 connects a cooling inlet 32 to the annulus 34 which resides between the casing 16 and the tubing string 19 of the well 11. A Valve 33 may be interposed in the cooling inlet 32 to regulate flow therethrough. If the tank 28 is pressurized, or for other reasons, the pump 29 may be excluded from the present system. In this instance, a valve to regulate coolant ow can be substituted for the pump 29.

Normally, the cooling inlet 32 is employed to carry coolant from the tank 28 into the annulus 34 and thereby control temperatures within the well 11 when it becomes heated by uids from the formation 13.

A controller 36 is interconnected between the pressure sensor 24 and the pump 29. The controller 36 may be of any construction which can receive a signal and as a result begin operation of a motor-driven pump or the like. The pressure sensor 24 is arranged so as to provide a signal to the controller 36 in response to a change in pressure of the uid contained in the conduit 22 when the temperature of the fluids entering the well 11 reach a specified temperature. The signal may be hydraulic, pneumatic, or electrical in nature. For example, the tiuid within the conduit 22 may provide a certain elevated pressure to activate the pressure sensor 24 when the flow of uids from the formation 13 has reached a specified temperature of, for example, 450 F. However, some other temperature may be used to activate the pressure sensor 24. Upon receiving the signal from the pressure sensor 24, the controller 36 activates the pump 29, or control valve, as the case may be. At this time, coolant from the tank 28 is moved through piping 26 into the coolant inlet 32 and enters the annuius 34 of the well 11. The amount of fluid flowing into the annulus 34 can be adjusted by the valve 33 to maintain the temperature within the well 11 below the specified temperature.

When the temperature in the annulus 34 has been reduced to a desired value, the pressure of the fluid within the conduit 22 will decrease suiciently below the selected temperature to di-activate the pressure sensor 24. At this condition, the signal from the pressure sensor 24 to the controller 36 is terminated and shuts down operation of the pump 29. Whenever the temperature again rises to the specified temperature, the pressure sensor 24 is again activated to apply a signal to the controller 36 and begin operation of the pump 29. This alternate cycling of the pump 29, only as needed, insures an adequate flow of coolant into the annulus of the well 11 to maintain temperatures therein below the selected temperature. However, excessive amounts of coolant are not introduced into the well 11 with this arrangement.

It can be seen that the employment of the conduit 22 with the heat-expansive uid therein as the signaling source of a selected temperature Within the well 11 is of great advantage. No electrical conductors need be contained within the well 11 Where they can be damaged by corrosion and heat action. Additionally, the surface facilities can be of a simple nature. Similarly, it is of great advantage that the coolant which is introduced into the well 11 can also be the uid which is employed in the conduit 22 to produce the pressure rise that activates the sensor 24. Thus, the signal which reflects the need of cooling the well 11 is also derived from the same material asis employed for cooling the well 11.

Where an introduction of coolant through the conduit 22 into the well 11 is desired, the system of this invention may be modified in the following manner. One or more pressure relief valves 37 are uidly connected to the conduit 22 below the check valve 27. The pressure relief valves 37 may be of any construction and set to open at a first pressure which represents the expansion of the fluid in the conduit 22 when subject to a selected temperature of the fluids from the formation 13. Also, the pressure relief valves 37 are set to close tat a value lower than the first pressure. The pressure relief valves 37 are adjusted in the open-closed pressure range to remain closed at the normal pressure within the conduit 22 represented by temperatures below a selected temperature. For example, a pressure rise of the fluid within the conduit 22 in an amount of a hundred pounds above the normal pressure may be required to open the pressure relief valves 37. However, the pressure of the uid within the conduit 22 may fall to fifty pounds below the normal pressure to close the pressure relief valves 37` The desired functioning of these valves 37 may be provided by spring loading, temperature sensitive elements, or other mechanism.

A change in fluid pressure in the conduit 22 occurs once the pressure relief valves 37 are opened. As a result, the pressure sensor provides a signal to activate the pump 29. Thus, coolant is passed continuously from the tank 28 into the annulus 34 at above normal or static pressure but somewhat below the pressure required to open these valves.

It may be desired that the coolant is introduced intermittently into the well 11 when using these valves. Under these circumstances, the controller 36 may be arranged, at given intervals, to cle-activate the pump 29, or flow control valve, in the piping 26 and thereby terminate the flow of coolant. Under these conditions, uids will be vented from the conduit 22 through the pressure relief valves 37 until the pressure therein has decreased to a suicient level that these valves will automatically close. Coolant will again till the conduit 22 through check valves 27 to normal operating pressure. At this time, the conduit 22 has been restored to its original operating condition. Then, if the temperature of the fluids entering the well 11 again reach the selected temperature, the pressure relief valves 37 will be opened due to the pressure build-up within the conduit 22. Then, the coolant again will be introduced into the well 11. Any suitable mechanism for intermittently, or for selected intervals, terminating the flow of coolant into the well 11 may be employed for this purpose.

If desired, the change in pressure of the uid in the conduit 22 may -be used in the pressure sensor 24 to generate a signal by which the controller 36 initiates operation of the pump 29, or to open the valve 33 in coolant inlet 32, or both. The coolant thus may flow in the conduit 22 and the coolant inlet 32.

As there are many possible embodiments which may be made of the present system without departing from the spirit of the present invention, it is to be understood that all matters herein set forth and shown in the accompanying drawing are to be interpreted as illustrative and not in a limiting sense. The appended claims define the scope of the present invention.

What is claimed is:

1. In a Well having an open production interval in a carbonaceous formation and adapted for the recovery therefrom of products of a thermal recovery procedure, the system comprising:

(a) a tubing string in said well having an inlet therein and arranged for the withdrawal of said products from said formation to the earths surface;

(b) a conduit mounted adjacent said tubing string and having its lower extremity sealed to fluids;

(c) a heat-expansible liuid filling said conduit;

(d) at least one pressure relief valve uidly interconnected with said conduit, said valve being closed when the pressure of said fluids in said conduit refiects a temperature less than a specified temperature and opened at an increased pressure when said fluid refiects a temperature greater than said specified temperature to vent fluid from said conduit into said well; and

(e) ow control means connected to said conduit at its upper extremity for introducing a coolant into said conduit at a pressure sufficient to hold open said pressure relief Valve after said valve has been once opened upon occurrence of a pressure drop in said conduit when fluid is vented therefrom.

2. The system of claim 1 wherein a plurality of pressure relief valves are spaced along said conduit adjacent the production interval.

3. The system of claim ll wherein said lioW control means receives from a pressure sensor fluidly connected to said conduit a signal representative of a change in pressure when said pressure relief valve vents fiuid from said conduit, and said fiow control means activate a fluid pumping means connected to said conduit in response to said signal to introduce collant into said well.

4. The system of claim 3 wherein said pressure relief valve operates to generate a first pressure signal representative of its opening, and said first pressure signal activates said pressure sensor.

5. In a well having an open production interval in `a carbonaceous formation and adapted for the recovery therefrom of products of a thermal recovery procedure, the system comprising:

(a) a tubing string in said well having an inlet therein and arranged for the Withdrawal of said products from said formation to the earths surface;

(b) a conduit mounted coaxially adjacent said tubing string and having its lower extremity sealed to fiuids;

(c) a heat-expansible uid filling said conduit;

(d) a coolant inlet conduit means uidly connected to the annulus about said tubing string in said well;

(e) at least one pressure relief valve fluidly interconnected with said conduit, said valve being closed when the pressure of said fluids in said conduit refiects a temperature less than a specified temperature and opened at an increased pressure when said uid reects a temperature greater than said specified temperature to vent uid from said conduit into said well;

(f) a pressure sensor fluidly connected to said conduit to provide a signal representative of a change in pressure of said fluid in said conduit upon a temperature being obtained in said well greater than a specified temperature; and

(g) flow control means connected to said conduit means for introducing a coolant into said annulus of said well surrounding said tubing string in response to said signal provided by said pressure sensor.

6. The system of claim 5 wherein said pressure sensor provides a signal representative of the pressure change occurring when said pressure relief valve vents uid from said conduit, and said flow control means activate for certain intervals a fluid pumping means connected to said conduit means in response to said signal to introduce coolant into said well.

7. In a well having an open production interval in a carbonaceous formation and adapted for the recovery therefrom of products of a thermal recovery procedure, the system comprising:

(a) a tubing string in said well having an inlet therein and arranged for the withdrawal of said products from said formation to the earths surface;

(b) a conduit mounted in juxtaposition adjacent said tubing string and having its lower extremity sealed to fluids;

(c) a heat-expansible iiuid filling said conduit;

(d) coolant inlet conduit means fiuidly connected to said annulus about said tubing string in said well;

(e) a pressure sensor uidly connected to said conduit to provide a signal representative of a change in pressure of said fluid in said conduit upon a temperature being obtained in said well greater than a specified temperature; and

(f) flow control means connected to said conduit means for introducing a coolant into said annulus of said well upon occurrence of said signal.

8. The system of claim 7 wherein said pressure sensor provides a signal representative of the pressure change occurring in said conduit, and said flow control means activate operation of a fluid pumping means connected to said conduit means in response to said signal thereby introducing coolant into said well.

9. In a well having an open production interval in a carbonaceous formation and adapted for the recovery therefrom of products of a thermal recovery procedure, the system comprising:

(a) a tubing string in said well having an inlet therein and arranged for the Withdrawal of said products from said formation to the earths surface;

(b) a conduit mounted in juxtaposition adjacent said tubing string and having its lower extremity sealed to fluids;

(c) a heat-expansible fluid filling said conduit;

(d) coolant inlet conduit means fiuidly connected to said annulus about said tubing string in said Well;

(e) a pressure sensitive means fluidly connected to said conduit to provide a signal representative of a change in pressure of said uid in said conduit upon a temperature being obtained in said well greater than a specified temperature; and

(f) iiow control means connected to said conduit means for introducing a coolant into said annulus of said Well upon occurrence of said signal.

10. The system of claim 9 wherein said pressure sensitive means is a pressure sensor which provides a signal representative of the pressure change occurring in said conduit, and said flow control means activate operation of a iiuid transferring means connected to said conduit means in response to said signal thereby introducing coolant into said well.

References Cited UNITED STATES PATENTS 3,127,319 3/1964 Natland 166--57 3,142,336 7/1964 Doscher 166-57 3,160,208 12/1964 lorda 166-57 3,357,490 l2/1967 Holmes 166-57 JAMES A. LEPPINK, Primary Examiner.

U.S. Cl. X.R. 166-57 

